The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.
This present invention relates generally to current sensors, and more specifically the invention pertains to a high current, wide dynamic range sensor. Giant Magnetoratio (GMR) sensors detect current phenomena and ground faults in a power distribution circuit. Powered by a 20 V DC or AC source, the output of a solid state chip having a GMR sensor adjacent to a conductor is a full-wave rectified form of the current in the conductor. This is fed to the current sampling circuit of the electronic trip unit of a circuit breaker and can be used to trip the circuit breaker when overcurrent conditions are detected.
Examples of GMR current sensor applications are disclosed in the following U.S. patents, copies of which are attached to the Information Disclosure Statement submitted herewith, and incorporated herein by reference.
U.S. Pat. No. 3,621,334 issued to Burn et al.;
U.S. Pat. No. 4,425,596 issued to Satou;
U.S. Pat. No. 5,049,809 issued to Wakatsuki et al.;
U.S. Pat. No. 5,615,075 issued to Kim;
U.S. Pat. No. 5,923,514 issued to Scott et al.;
U.S. Pat. No. 5,729,137 issued to Daughton et al.;
U.S. Pat. No. 5,561,368 issued to Dovek et al.;
U.S. Pat. No. 5,831,426 issued to Black et al.;
U.S. Pat. No. 4,097,802 issued to Mazzeo et al.;
U.S. Pat. No. 4,414,510 issued to Milkovic;
U.S. Pat. No. 4,520,311 issued to Petr et al.;
U.S. Pat. No. 5,005,064 issued to Yoshino et al.;
U.S. Pat. No. 5,119,025 issued to Smith et al.;
U.S. Pat. No. 5,260,653 issued to Smith et al.;
U.S. Pat. No. 5,561,368 issued to Dovek et al.;
U.S. Pat. No. 5,122,227 issued to Ott;
U.S. Pat. No. 5,302,461 issued to Anthony;
U.S. Pat. No. 5,313,186 issued to Schuhl et al.;
U.S. Pat. No. 5,329,413 issued to Kondoh et al.;
U.S. Pat. No. 5,399,965 issued to Heberle;
U.S. Pat. No. 5,636,159 issued to A. Pohm;
U.S. Pat. No. 5,512,818 issued to Jin et al.;
U.S. Pat. No. 5,561,366 issued to Takahashi et al.
The above-cited patents are instructive in the technology. For example, they show a current sensor has a closed loop magnetic hoop with a gap and a central aperture for receiving a conductor. An IC chip incorporating a GMR sensor can be positioned in the gap to provide a measure of the current in the conductor. A relatively small current transformer provides the necessary information about the direction of the current to an electronic trip unit for a circuit breaker as well as power supply for the IC chip and the trip unit. The trip unit operates in the presence of AC and DC faults. In a three phase power system, a single GMR chip in the proximity of three closely spaced phase conductors, together with a current measurement from the neutral line, enable trip units to operate on the occurrence of AC and DC faults.
There are applications where accuracy over a wide dynamic range is required for current sensing. A need remains for a configuration where a wide range of current can be sensed accurately in spite of using a magnetic material with non-linearities and limited hysteresis. The present invention is intended to satisfy that need.
The present invention is a GMR high current, wide dynamic range sensor containing: a strip line current carrier, an IC chip containing a GMR sensor element, and an integrated drive coil, like an isoloop.
The cross section of the strip line, which could be on a PC card, or could be a wire, is external to an IC chip containing a GMR sensor element and an integrated drive coil, like the isoloop. Field produced by current in the strip line is detected by the sensor. Feedback field is produced by current in an on-chip coil. In many applications, the current in the strip line is large (say 10 Amps), while it is desirable to make the feedback current small. Also, if high accuracy is required over a large dynamic range, at low current level, spurious fields to magnetized bodies or current in other lines may limit the accuracy of the sensor.